Facebook today open-sourced Pop, the engine behind Paper’s smooth animations and transitions, over on GitHub. Pop uses dynamic instead of traditional static animations to control the scrolling, bouncing, and unfolding effects in the social news app.

Tsinteris adds, however, that his animation engine goes a level higher: “With Pop, we are able to keep the familiar and powerful programming model of Core Animation while also capturing a gesture’s velocity and better reflecting user intent.” He argues that touch interfaces have led to a new wave of software design, with direct manipulation of on-screen elements raising user expectations of the screen as a medium, and if objects respond to our touches, responding to the velocity of our flick is the next logical step.

Pop was designed with three goals in mind:

Commonly needed animations are “extremely convenient.” In addition to the four established static animations, Pop introduces three new primitive animation types: spring, decay, and custom. Spring is responsible for Paper elements’ attractive bounce while Decay brings movement to an eventual slow halt. Both take velocity as an input and realistically respond to user gestures.

It’s an extensible framework, meaning custom animation allows iOS developers to plug-in their own animation code, making it easier to create unique effects. By decoupling animation from display, the framework is of wide scope, allowing it to animate any property of any Objective-C object.

It’s a developer-friendly, yet powerful, programming model. Developers who know how to use Core Animation explicit animations will know how to use Pop.

The only way to see how well the above has been achieved is to give Pop a shot. Since it’s freely available, this one is a no-brainer.

Emil was a reporter for The Next Web between 2012 and 2014. Over the years, he has covered the tech industry for multiple publications, including Ars Technica, Neowin, TechSpot, ZDNet, and CNET. Stay in touch via Facebook, Twitter, and Google+.